The present invention pertains to a simple approach to obtain economical cruise control for aircraft. More particularly, the invention involves a method and apparatus to obtain performance data for maximum cruise economy on any particular aircraft.
It is normal that pilots will determine the best power settings for maximum range or most economical fuel used by referring to the Performance Data Charts usually found in the aircraft owner's manual published by the aircraft manufacturer. Normally such performance data is obtained by performance test of a new or prototype aircraft and then the data is published for use with all aircraft of that particular type and model. Of course, the prototype or test aircraft was probably new and with a new or very low time engine that was still capable of producing specified engine power. Usually no two production aircraft will come off of the assembly line weighing the same or performing exactly the same as the prototype aircraft for which the performance charts were developed. Also after the aircraft is sold each owner has a different taste in equipment and some may load their aircraft down with exotic equipment, some owners may keep their aircraft waxed thereby reducing drag, or keep the engine in perfect shape capable of producing maximum power for which it was designed. Then, of course, there are those who may modify the aircraft or use it in extremely adverse conditions or pay little or no attention to weight and balance and will have more drag in flight upon the aircraft than the average aircraft of that particular model. In addition, aircraft which have not had particular maintenance performed upon it within a short period of time will not produce precisely the average power which the prototype aircraft produced when designing the performance charts. So, it can be seen that few aircraft of the same type and model will have exactly the same performance as the prototype aircraft. All of this, or course, effects the operating characteristics of each particular aircraft. Another problem with the standard performance charts supplied by the aircraft manufacturer is that the charts are seldom used because of the inconvenience of handling and reading the performance charts in a crowded cockpit, especially at night, or when in weather under instrument flying conditions. Many times these charts are difficult to interpret and require reference to a second and third chart and/or use of a computer. Because of these inconveniences and because the charts do not exactly match the aircraft in question, most pilots waste considerable fuel by not flying at the proper power setting for the conditions under which the aircraft is being operated.